The present invention relates to a integrated type key top and key input device and computer using the same.
Conventionally, as a key input device of a computer, a word processor or the like, there has been a known one in which each key top is operated via a guide mechanism or a pantograph mechanism in closing its electric contact by depressing the key top.
In recent years, there has been a growing demand for reductions in size, weight and, above all, thickness of, in particular, portable computers of a notebook type and the like, and as part of this trend, it has been also required to further reduce in thickness the key input device.
However, in the case of the one employing the aforementioned conventional guide mechanism or pantograph mechanism, there is required a space in which such a mechanism is placed between the key top and the electric contact, and therefore, it is primarily difficult to achieve a sufficient reduction in thickness.
In view of the above, as disclosed in the document of Japanese Utility Model Laid-Open Publication No. HEI 6-38358, it can be considered to reduce the space between the key top and the electric contact as far as possible by connecting each key top to a peripheral frame portion via a hinge and operating the key top in a state in which the key top is supported by this hinge.
However, in the case of this hinge type, although the key input device can be further reduced in thickness by compacting the space below the key top (between the key top and the electric contact), it is required to take the following factors of, in particular, the hinge portion into consideration. The factors are: the strength (absolute strength capable of withstanding damage and the like due to the effect of an external force); durability (fatigue strength) with respect to repetitive key input operations; a required operating power in depressing the key; a reliability in switch operation with respect to a variation in operating force effecting position; a facility in manufacturing and assembling and so on. However, it has been very difficult to optimally set the dimensions (length, thickness, total width, etc.), position and so on of the hinge portion so that these factors are satisfied with a reduction in thickness of the key input device achieved.
In regard to the length of the hinge portion, each key portion is limited in size by the area of the keyboard, the key arrangement and the like, and each key top itself is required to have an area not smaller than a specified area in terms of the key input operability. Therefore, an interval between the frame portion and the key top is limited. The length of the hinge portion is normally defined by this interval between the frame portion and the key top, and therefore, it cannot be set longer than a specified length.
Furthermore, in regard to the thickness and width (sum total of width width of each hinge portion.times.number) of the hinge portion, both of them are preferably great in terms of securing the strength (absolute strength) of the hinge portion, but on the other hand, a key top depressing force increases, consequently reducing the operability.
In other words, the thickness of the hinge portion is preferably small in terms of the influence on the operating force, however, it had better be thick for the purpose of securing a strength (absolute strength). In general, the square of the hinge thickness effects on the durability directly influenced by a stress, and the cube of the hinge thickness effects on the operating force directly influenced by a spring force.
On the other hand, the width (sum total of width) of the hinge portion had better be narrow in terms of reducing the operating force, however, it had better be wide for the purpose of securing a strength (absolute strength). The hinge width effects linearly on the operating force directly influenced by the spring force. It is to be noted that, even if the hinge width is great, the hinge width produces a small effect on key operating forces in the transverse direction or a diagonal direction, which are normally not taken into consideration, and therefore, the absolute strength is influenced relatively less by the hinge width.
In regard to the position of the hinge portion (i.e., an argument about where to provide the hinge portion around the key top), in a case where the hinge portion is provided in a center portion of a specified side of the key top and an operating force is exerted on an end portion displaced in the hinge width direction from the center portion of the key top (in the case of so-called one-sided depressing), the other side end is disadvantageously lifted by a torsional deformation of the hinge portion, resulting in hardly closing the electric contact. That is, it is difficult to keep the reliability of the switch operation with respect to the variation in effecting position of the operating force. This becomes significant in the case of a horizontally elongated key top.
Furthermore, in the normal key input operation, a stroke of the key top is caused by a displacement about a point of the hinge portion fixed to the frame portion, and key top is displaced until its stroke motion will be regulated by a predetermined stopper portion. In other words, the displacement stroke of the key top is suppressed within a specified range by the operation of the aforementioned stopper portion, and therefore, provision of the hinge portion throughout the entire width of a side of the key top (i.e., not only at the end portions but also at a center portion of a side) exerts less favorable influence on the improvement of the durability (fatigue strength). The increase in hinge width rather requires an increased operating force, and if there is an attempt at avoiding this, the hinge thickness cannot help being reduced in thickness by that much, and this adversely causes a disadvantage of a difficulty in handling or the like when a separately formed hinge portion is incorporated.
As described above, it has been not so easy to optimally set the dimensions, position and so on of the hinge portion so that the aforementioned requirements are satisfied with a reduction in thickness of the key input device achieved.